The speed of metal-oxide-semiconductor (MOS) transistors is closely related to the drive currents of the MOS transistors, which drive currents are further closely related to the mobility of charges. For example, n-type transistors have high drive currents when the electron mobility in their channel regions is high, while p-type transistors have high drive currents when the hole mobility in their channel regions is high.
Compound semiconductor materials of group III and group V elements (referred to as III-V compound semiconductors hereinafter) are good candidates for forming transistors due to their high electron mobility. Therefore, III-V compound semiconductor based transistors have been explored. III-V compound semiconductor films, however, typically need to be grown on other substrates because it is difficult to obtain bulk III-V compound semiconductor crystals. The growth of III-V compound semiconductor films on dissimilar substrates faces difficulties because these substrates can have lattice constants and thermal expansion coefficients different than that of the III-V compound semiconductors. Various methods have been used to form high quality III-V compound semiconductors. Fin Field-Effect Transistors (finFETs) can be formed based on resulting III-V compound semiconductors.